Multiple: Hives

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

Hives refers to an eruption of wheals (flat-topped itching or stinging bumps, welts, or patches) on the skin following contact with an allergen or some other physical agent. It is not a single disease but rather a pattern of reaction to an irritant of some kind. Hives may be caused by infections, medications, insect bites, chemicals, food allergies, underlying medical disorders, or a variety of other causes. Hives that last less than six weeks are defined as acute urticaria; hives that are present for six weeks or longer or that recur frequently are known as chronic urticaria.

Description

Hives are pale, itchy, or stinging welts or wheals that form on the skin, most commonly as a reaction to an irritant. Hives located near the mouth, eyes, or genitals may cause the lower layers of nearby skin to swell up or look puffy—this reaction is known as angioedema.

Hives vary in size from about a quarter-inch in diameter to six inches or even larger. They can also join together to form even larger patches of

raised skin with clearly defined edges. They will turn white when the center of the wheal is pressed. They may appear suddenly, change shape, and disappear within hours or even minutes. Hives, after disappearing, do not leave scars on the skin.

Acute hives are typically caused by an allergic reaction to foods or medications, fresh foods being more likely to cause hives than cooked foods. The most common “problem” foods are nuts, chocolate, fish and shellfish, tomatoes, eggs, fresh berries, soy, wheat, and milk. Almost any medication can cause hives in a susceptible person. The common offenders are aspirin and ibuprofen; penicillin and other antibiotics; codeine and pain relievers containing codeine; and medications given to treat high blood pressure. Other triggers of acute hives include certain substances, particularly latex; pollen, molds, and animal dander; infections, particularly the common cold; and insect bites.

Some cases of acute hives are triggered by physical causes, such as exposure to sunlight, hot weather, cold water, or exercise. Hives resulting from sun exposure usually fade in one to two hours. Some people who get hives after swimming in cold water may feel faint or dizzy as well. A few people get hives when their skin is scratched or stroked firmly. This condition is called dermatographism and can occur together with hives caused by allergens.

Chronic hives last for longer than six weeks. The causes of chronic urticaria are usually more difficult to identify than the causes of acute

hives. They often include autoimmune disorders like lupus or Hashimoto disease, or bacterial or fungal infections. In the majority of cases, however, the cause of chronic hives is never discovered. Chronic hives may last for months or even years and have a severe impact on the patient's quality of life.

Demographics

Hives are a common skin problem in North America, affecting between 20 and 25 percent of people at some point in their lives. As far as is known, hives are equally frequent in all races and ethnic groups, although they are more common in women—there are three females for every two males affected. Chronic urticaria is less common that acute urticaria, affecting between 1 and 3 percent of the population. Dermatographism affects about 5 percent of the general American population.

Acute hives can develop in people of any age, but are most common in teenagers and young adults in their twenties. Chronic hives, on the other hand, are more common in middle-aged adults.

Causes and Symptoms

The basic cause of hives is the release of a chemical called histamine. The histamine causes small blood vessels to leak plasma (the liquid part of blood) into the skin, causing the surface of the skin to rise and form wheals or angioedema.

Home Treatment for Hives

While waiting for antihistamine and other medications to take effect, patients with hives can do the following to relieve itching and speed the healing of their skin:

• Avoid taking hot baths or showers; use lukewarm water instead.
• Avoid using harsh or heavily perfumed soaps.
• Stay out of direct sunlight during the hottest hours of the day; exercise during the early morning or early evening.
• Avoid heavy exercise in hot weather or any activity that might cause sweating, as perspiration can make hives worse.
• Wear light, loose-fitting clothing.
• Apply cool compresses to the affected area.
• Try to work or sleep in a cool room.
• Lower the stress level if possible.

If any of the following symptoms appear with hives, a doctor should be contacted at once or the patient taken to an emergency room:

• Dizziness or fainting
• Difficulty in breathing or swallowing
• Wheezing
• Tightness or pain in the chest
• Swelling of the tongue, lips, or entire face
• Nausea, vomiting, abdominal cramps, or diarrhea

The symptoms of hives are itching, stinging, and burning on the affected parts of the skin. In some cases, angioedema can affect the tissues that line the throat, causing the airway to swell shut and make it difficult to breathe or swallow. This type of angioedema is a medical emergency and requires immediate treatment in an emergency room.

Diagnosis

Diagnosis of the cause of acute hives is usually helped by asking patients about their food or medication history, recent exposure to sun or insect bites, recent infections, or their occupation. Patients may be asked to keep a record of the foods they eat, the medications they use, and the types of exercise they do on a regular basis. Doctors may also ask patients to keep a record of the location of the hives when they appear and how long the individual hives last.

Although it is usually not necessary to test for the causes of acute hives in order to treat the problem, the doctor may order skin tests to see whether specific foods, medications, or chemicals are triggering the hives. In some cases the hives may have more than one cause. Blood tests may be ordered to test for the possible causes of chronic hives. A primary care doctor may refer the patient to a dermatologist (a specialist in skin diseases) for more detailed tests or to make sure that the patient does not have a different type of skin disease.

Treatment

Acute hives can often be treated at home by a combination of antihistamine medications prescribed by the doctor, avoiding known triggers, and protecting the skin against further irritation (see sidebar). If the hives are not relieved by antihistamines, the doctor may prescribe cortisone or other steroid medications, but these should be used only for short periods of time.

Patients who have severe attacks of hives or angioedema are usually given an injection of adrenaline to clear the airway and are taken to a hospital emergency room. People who have repeated episodes of angioedema that cause breathing problems are usually given an EpiPen, which is a device that contains adrenaline, so that they can inject themselves in an emergency.

Patients whose hives appear to be triggered by emotional stress may be helped by relaxation techniques or stress management programs.

Prognosis

The prognosis of hives depends on the cause and whether the hives are acute or chronic. Acute hives often clear up rapidly once the allergen or other cause of the skin reaction has been removed. Chronic hives, however, can be difficult to treat or cope with, particularly if the skin eruptions are related to an autoimmune disorder. One study found that

chronic hives lasted a year or longer in more than 50 percent of patients and 20 years or more in 20 percent of them.

Prevention

There is no known way to prevent all possible types of hives, although avoiding foods and medications known to trigger acute hives can help. The limitation of this approach, however, is that specific triggers cannot be identified in about 50 percent of cases.

Another recommendation is to cut down on alcoholic beverages—they can make the itching of hives worse or even trigger hives in some people. Some patients are also advised by their doctors to take antihista-mines on a daily basis in order to prevent acute attacks of hives.

The Future

Both acute and chronic hives are likely to be common skin problems for the foreseeable future. It may be that further research will shed light on the causes of chronic hives so that more effective treatments can be developed.

WORDS TO KNOW

Adrenaline: A hormone that can be used in medicine to open the breathing passages in patients with severe angioedema. It is also called epinephrine.

Allergen: Any substance that can provoke an allergic reaction in susceptible individuals.

Angioedema: The medical term for the swelling of tissues around the eyes, lips, and genitals that sometimes accompanies hives.

Chronic: Long-term or recurrent.

Dander: Tiny skin, feather, or fur particles from household pets that cause allergic reactions in some people.

Dermatographism: A type of hives produced by scratching or stroking the skin.

Dermatologist: A doctor who specializes in diagnosing and treating diseases of the skin.

Histamine: A compound that is released during an allergic reaction.

Urticaria: The medical term for hives.

Wheal: A suddenly formed flat-topped swelling of the skin; a welt.

SEE ALSO Allergies; Anaphylaxis; Hashimoto disease; Lupus

For more information

BOOKS

Wanderer, Alan A. Hives: The Road to Diagnosis and Treatment of Urticaria: A Workbook and Resource for Healthcare Professionals and Patients. Bozeman, MT: Anson Publishing, LLC, 2004.

PERIODICALS

Roth, Sharon. “A Shot in Time.” New York Times, May 14, 2006. Available online at http://query.nytimes.com/gst/fullpage.html?res=9C0DE5DA173EF937A25756C0A9609C8B63&sec=&spon=&pagewanted=all (accessed May 12, 2008). This is an article about the use of the EpiPen to treat emergency episodes of angioedema.

WEB SITES

American Academy of Dermatology (AAD). Urticaria—Hives. Available online at http://www.aad.org/public/publications/pamphlets/skin_urticaria.html (updated September 2005; accessed May 12, 2008).

Mayo Clinic. Chronic Hives (Urticaria). Available online at http://www.mayoclinic.com/health/chronic-hives/DS00980 (updated June 22, 2007; accessed May 11, 2008).